Electric discharge tube



Aug. 24, 1948. N. WARMOLTZ ELECTRIC DISCHARGE TUBE Filed Feb. 12, 1947N- WAR MOLT Z INVENTOR AG'ENT Patented Aug. 24 1948 ELECTRIC DISCHARGETUBE? Nicolaas Warmoltz,

signor to Hartford Company, Hartford,

1 Claim.

This invention relates to an electric discharge tube comprising a liquidor a solid cathode and an ignition electrode constituted by a.non-insulating member surrounded by insulating material which is, inpart, contained in the cathode. The non-insulating material may be aconductor or a. semi-conductor; furthermore the insulator may contain agas which breaks down at a high voltage.

In tubes provided with the aforesaid ignition electrodes the ignition isset up by a spark produced in the narrow slit between the ignitionelectrode and the cathode surface, which in the case of a liquid cathodeis generated owing to the capillary depression, on a high, generallypositive voltage being placed on the conductor. This is the reason whythese ignition electrodes are referred to as spark strikers.

Generally speaking, tubes comprising spark strikers operatesatisfactorily, but only for a short time. Generally, a thin layer ofprecipitate is formed on the outside of the ignition electrode and thislayer prevents a spark initiating the ignition from being produced. Thebreakdown of the striker may be remedied by raising the ignitionvoltage, but generally only for a short time.

In an electric discharge tube according to the invention, comprising aliquid or a, solid cathode and an ignition electrode constituted by anon-insulating member surrounded by insulating material which is, inpart, enclosed in the oathode, the ignition electrode above the cathodesurface down to a short distance therefrom is coated with anon-insulating layer. The distance between the cathode surface and thenoninsulating layer on the ignition electrode ranges from a fewmillimeters to a few centimeters in accordance with the variations ofthe cathode level and the voltage applied to the ignition electrode, andalso with the height up to which the ignition electrode in tubes of thetype concerned is covered with a layer of precipitate. The noninsulatinglayer mounted on the striker may have very heavy resistance and hencealso semiconductors may be used. The non-insulating layer must bemounted so as to make contact with the precipitate formed. According tothe invention it has been found that tubes provided with an ignitionelectrode according to the invention act reliably for a long time; thesatisfactory operation may be due to the layer-of dirt formed on theignition electrode being burnt off by the supply current passing throughor by jump-over sparks before this layer can affect Eindhoven,Netherlands, as-

National Bank and Trust Conn, as trustee Application February 12, 1947,Serial No. 728,108 In the Netherlands July 29, 1944 Section 1, PublicLaw 690, August 8, 1946 Patent expires July 29, 1964 the ignition, sincethis does not occur in the case of minute thickness. As an alternative,it may be that the layer of dirt jointly with the conductive layer onthe ignition electrode starts to act as a resistance striker, with theresult that the ignition electrode keeps on playing its partnevertheless; the layer of dirt may in this case be burnt awaynevertheless.

It has been suggested before to make ignition electrodes constituted bya stud of insulating material partly immerged in the cathode liquid andcoated down, to a few centimeters distance from the cathode surface witha metal layer.

, The insulating stud contains a conductor which is not connected. tothe supply wire for the ignition electrode, but which may be connectedto the cathode. In this case the ignition is set up by jump-over sparksalong the surface of the insulating stud.

Spark strikers are known in which the supply wire of the spark strikerinside the tube is not coated with insulating material and is deformedto form an auxiliary anode for the improvement of the ignition. Thisuncoated supply wire is, however, spaced away too far from the cathodesurface to be able to accomplish the same function as the conductivelayer of the ignition electrode according to the invention.

In order that the invention may be clearly understood and readilycarried into effect, it will now be set out more fully with reference tothe accompanying drawing, which illustrates an electric discharge tubecomprising an ignition electrode according to the invention.

Referring to the single figure of the drawing, i designates the wall ofthe discharge tube inside of which are enclosed the cathode 2 of mercuryand the anode 3 of carbon. The ignition electrode is constituted by a,quartz tube 5 which is partly filled with a supply of mercury 6 whichmakes contact with a supply wire 4. The top of the ignition electrode iscoated with a thin layer of nickel I which is also connected with thesupply wire 4. The quartz tube 5 has a wall thickness of 0.5 mm.; theignition voltage has a value of about 8000 volts. Thanks to theapplication of the conductive layer 1 the tube operates reliably for aconsiderably longer period than would be the case without this layerbeing provided on the striker, for example two or three times as long.

What I claim is:

An electric discharge tube having a liquid cathode and an ignitionelectrode constituted by a conducting member surrounded by insulatingma- 3 4 terial which is, in part, immersed in the cathode, and the partof the ignition electrode that REFERENCES CITED is out of the cathodebeing coated to a, short The following references are of record in thedistance from the cathode surface with a nonfile of this patent:

insulating layer which is conductively connected 5 to the conductor ofthe striker. FOREIGN PATENTS Number Country Date NICOLAAS WARMOLTZ.506,376 Germany Nov. 23, 1927

